Black currant seed oil is derived from the seeds of the plant Ribes nigrum. It is a rich source of the n-6 (omega-6 ) polyunsaturated fatty acid gamma-linolenic acid (GLA). Black currant seed oil contains about 15 to 20% GLA. The n-3 (omega-3) polyunsaturated fatty acid alpha-linolenic acid (ALA) is also present in blackcurrant seed oil (12 to 14%) as is the fatty acid linoleic acid. Also present, in smaller amounts, is stearidonic acid. The various fatty acids are found in blackcurrant seed oil in the form of triacylglycerols, also known as triglycerides. GLA is concentrated in the sn-3 position in blackcurrant seed oil as it is in evening primrose oil.

The terms black currant seed oil and black currant oil are used interchangeably.
According to a study published in February 2000 by researchers at Tufts University in Boston, 4.5 gm daily of black currant seed oil was able to promote cell-mediated immune function. In addition, a similar study found that black currant seed oil had an immune-enhancing effect attributable to its ability to reduce prostaglandin E production. Other studies have found that the extract has anti-inflammatory properties due to its capability of stimulating the production of prostaglandin-1, an anti-inflammatory hormone.